Objective: To investigate the opsin expression in form-deprived and defocus myopia in guinea pig and to study the relationship between the opsin expression and the experimental myopia.
Methods: Fifty guinea pigs were randomized into form-deprived group, defocus group (n = 20 in each group) and normal group (n = 10). Guinea pigs in form-deprived group wore a diffuser RGP on one eye since one week after birth. Those in defocus group wore -4.00 D RGP on one eye. The contralateral eyes wore 0 D RGP were used as the control. Refraction, axial length and depth of vitreous cavity were measured after 1 and 2 weeks. Animals were sacrificed and the retina were dissected at 10:00 - 12:00 AM. The level of opsin and its mRNA were measured by Western-blot and real-time PCR, respectively.
Results: Two weeks after the experiment, the refraction in form-deprived group and defocus group were (-4.00 ± 0.87) and (-2.00 ± 1.17) D respectively, which were significant different compared with contralateral eyes or normal control group (F = 203.98, 88.66, P < 0.05). These also accompany with increase of axial length and depth of vitreous cavity in form-deprived group and defocus group. Expression of S-opsin mRNA were increased both in form-deprived and defocus groups and the ratios of S-opsin mRNA/β-actin expression were 0.752 ± 0.05 and 1.117 ± 0.13 in two weeks treatment, which were significant different from contralateral eyes (the ratios of S-opsin mRNA/β-actin expression were 0.536 ± 0.04 and 0.772 ± 0.10.t = 6.10, 6.28, P < 0.05). Similar findings were also demonstrated in the expression of L-opsin mRNA, which were increased in form-deprived group and defocus group (the ratios of L-opsin mRNA/β-actin expression were 0.42 ± 0.01) compared with contralateral eyes (the ratios were 0.24 ± 0.0 and 0.34 ± 0.04. t = 6.30, 4.93, P < 0.05) after two weeks experiment. The western-blot results also indicated the high expression of S-opsin and L-opsin level compared to contralateral eyes in form-deprived and defocus groups.
Conclusions: Cone might be the detector receiving the signal of form-deprivation and defocus. Changes of opsin expression might play a role in the occurrence of experimental myopia in guinea pig.